This invention relates to measuring the ground resistance of an ungrounded power circuit in general and more particularly to a circuit for measuring the ground resistance in a d-c system supplied from a converter circuit.
By continuously measuring the ground resistance, a degradation of the insulation between ground and an ungrounded power circuit can be detected even before a short to ground actually occurs. In a measurement of the ground resistance of an ungrounded power circuit, the measurement result can be falsified by the ground capacity of the latter, the magnitude and distribution in space of which are not known.